Liquid discharging apparatus and method for discharging liquid

Abstract

To eliminate influence of discharge amounts depending on changes in liquid level of a liquid storage tank and to improve discharge accuracy of a liquid discharging apparatus. By a pressure regulating opening portion for forming a reference liquid surface maintaining a given pressure, pressure inside a pump chamber before a discharging operation is kept constant without affecting liquid level existing in the liquid storage tank. Therefore, volume of the inside of the pump chamber is kept constant and liquid can be discharged with higher precision.

What is claimed is:  
     
       1. A liquid discharging apparatus comprising: 
       a pump body incorporating an elastically deformable pump member therein and having a pump chamber expanding and contracting by said pump member;  
       an inflow passage provided between said pump chamber and a liquid storage tank containing liquid, and provided with such an inflow side valve as to open when said pump member executes an operation of a suction stroke;  
       a pressure regulating passage provided between said pump chamber and a pressure regulating opening portion, and provided with such a pressure regulating valve as to open when said pump member executes a discharging operation of an exhaust stroke and to keep pressure inside said pump chamber constant; and  
       a discharge passage provided between a discharge nozzle and said pump chamber, and provided with such a discharge side valve as to open when said pump member executes an operation of a discharge stroke.  
     
     
       2. The liquid discharging apparatus according to  claim 1 , wherein said pressure regulating opening portion is open to atmosphere at a position higher than liquid level of said liquid storage tank, and the pressure inside said pump chamber through said pressure regulating passage is set to be higher than when the operation of the suction stroke is completed. 
     
     
       3. The liquid discharging apparatus according to  claim 2 , wherein said pressure regulating opening portion is practically opened downwards and maintains a reference liquid surface by forming an interface depending on surface tension of the liquid. 
     
     
       4. The liquid discharging apparatus according to  claim 2 , wherein said pressure regulating opening portion is practically opened upwards. 
     
     
       5. A liquid discharging apparatus comprising: 
       a pump body incorporating an elastically deformable pump member therein and having a pump chamber expanding and contracting by said pump member;  
       an inflow passage provided between said pump chamber and a liquid storage tank containing liquid, and provided with such an inflow side valve as to open when said pump member executes an operation of a suction stroke;  
       a pressure regulating passage provided between a pressure regulating opening portion and said pump chamber, and provided with such a pressure regulating valve as to open after the operation of the suction stroke of said pump member is completed and that sets pressure of the inside of said pump chamber to be lower than when the operation of the suction stroke is completed; and  
       a discharge passage provided between a discharge nozzle and said pump chamber, and provided with such a discharge side valve as to open when said pump member executes an operation of a discharge stroke.  
     
     
       6. The liquid discharging apparatus according to  claim 5 , wherein the pressure regulating opening portion is open to atmosphere at a position lower than liquid level of said liquid storage tank. 
     
     
       7. The liquid discharging apparatus according to  claim 6 , wherein said pressure regulating opening portion is practically opened downwards and maintains a reference liquid surface by forming an interface depending on surface tension of the liquid. 
     
     
       8. The liquid discharging apparatus according to  claim 6 , wherein said pressure regulating opening portion is practically opened upwards. 
     
     
       9. The liquid discharging apparatus according to  claim 5 , wherein said pressure regulating opening portion is practically opened downwards and maintains a reference liquid surface by forming an interface depending on surface tension of the liquid. 
     
     
       10. The liquid discharging apparatus according to  claim 5 , wherein said pressure regulating opening portion is practically opened upwards. 
     
     
       11. The liquid discharging apparatus according to  claim 1 , wherein said pressure regulating opening portion is practically opened downwards and maintains a reference liquid surface by forming an interface depending on surface tension of the liquid. 
     
     
       12. The liquid discharging apparatus according to  claim 1 , wherein said pressure regulating opening portion is practically opened upwards. 
     
     
       13. A method for discharging liquid, in which liquid inside a liquid storage tank is discharged into a discharge nozzle by a sucking operation and a discharging operation executed by an elastically deformable pump member incorporated in a pump body and forming a pump chamber, the method comprising: 
       a sucking step of making said pump member executing an operation of a suction stroke as a condition that an inflow side valve is opened, said inflow side valve being provided in an inflow passage connecting said liquid storage tank and said pump chamber;  
       an exhausting step of opening a pressure regulating valve and making said pump member executing a discharging operation of a predetermined exhaust stroke with pressure inside said pump chamber keeping constant, said pressure regulating valve being provided in a pressure regulating passage connecting a pressure regulating opening portion and said pump chamber; and  
       a discharging step of opening a discharge side valve and making said pump member executing an operation of a discharge stroke, said discharge side valve being provided in a discharge passage connecting said discharge nozzle and said pump chamber.  
     
     
       14. A method for discharging liquid, in which liquid inside a liquid storage tank is discharged into a discharge nozzle by a sucking operation and a discharging operation executed by an elastically deformable pump member incorporated in a pump body and forming a pump chamber, the method comprising: 
       a sucking step of making said pump member executing an operation of a suction stroke as a condition that an inflow side valve is opened, said inflow side valve being provided in an inflow passage connecting said liquid storage tank and said pump chamber;  
       an exhausting step of opening a pressure regulating valve and setting pressure inside the pump chamber to be lower than when the operation of the suction stroke is completed, said pressure regulating valve being provided in an pressure regulating passage connecting a pressure regulating opening portion and said pump chamber; and  
       a discharging step of opening a discharge side valve and making said pump member executing an operation of a suction stroke, said discharge side valve being provided in a discharge passage connecting said discharge nozzle and said pump chamber.